MBBR Biofilm Formation Problems? Why Your Media Isn’t “Growing” and How to Fix It

Bywatertech

In the wastewater treatment industry, we often hear a common complaint: “I’ve been running my MBBR system for 30 days, but the media is still clean. Your carriers must be defective!”

As a manufacturer supporting projects in 50+ countries, I understand the frustration. However, unless the media is physically disintegrating, “failure to hang film” is rarely a material defect. It is almost always a commissioning error.

Today, I’m sharing a real-world case study from our engineering team at HNS Water Tech to show you why “Startup Lag” happens and how to fix it.

📉 Case Study: The “Starving” Biofilm

A client recently contacted us ready to return a batch of HDPE media. After a month of debugging a domestic sewage tank, there was zero biofilm growth.

The Site Conditions:

  • Influent: Low Load (COD ~200 mg/L)
  • Temperature: 15°C (Winter conditions)
  • Strategy: Inoculated with high Activated Sludge (MLSS 4,000 mg/L) + High Aeration (DO > 4 mg/L).

The Diagnosis: Why it failed?

  1. Ecological Competition: Biofilm and suspended sludge compete for the same “food.” With a massive army of suspended bacteria (4,000 mg/L MLSS) and limited food (200 mg/L COD), the suspended sludge consumed everything before the biofilm could even colonize the carrier.
  2. Excessive Shear Force: A DO of 4 mg/L creates violent turbulence. For young, fragile biofilm, this acts like a sandblaster, scouring microbes off the smooth plastic surface before they can stick.

🛠️ 4 Steps to Accelerate MBBR Biofilm Formation

If you are using standard HDPE/K1 media, you must follow these biological laws:

  1. Lower the MLSS: Reduce suspended sludge to 1,000–1,500 mg/L. Force the bacteria to find a “home” on the media to survive.
  2. Optimize Aeration: Drop DO to 1–2 mg/L. You need a gentle “boiling” effect, not a storm.
  3. Carbon Supplementation: If influent COD is <200 mg/L, add a carbon source (like glucose or sodium acetate) to keep COD >500 mg/L during the first 7-14 days.
  4. Temperature Awareness: At 15°C, standard hydrophobic plastic requires a 3-4 week induction period.

🚀 The Innovation: Eliminating the “Induction Phase” with HPU Media

What if you could bypass these strict operational requirements?

At HNS Water Tech, we developed HPU (Hydrophilic Polyurethane) Sponge Media to solve the inherent flaws of traditional plastic.

FeatureStandard HDPE MediaHNS HPU Sponge Media
Surface PropertyHydrophobic (Repels water)Hydrophilic (Water-attracting)
Startup Time20-30 Days5-7 Days
Micro-environmentExposed to shear forceProtected microporous structure
Expansion Rate0%Expands 1.7x for higher surface area

Why HPU changes the game:

  • Instant Affinity: It absorbs water instantly, providing a “sticky” surface for bacteria.
  • Zero Competition: The internal pores protect the biofilm from being washed away by high DO or outcompeted by suspended sludge.
  • Plug & Play: It is far more forgiving of operational errors during startup.

💡 Final Thought

If your MBBR isn’t performing, don’t rush to blame the plastic. Check your Food-to-Microorganism (F/M) ratio, check your DO, and stop starving your biofilm.

Or, choose a media designed to work with nature, not against it.

Need a technical audit of your MBBR process?
👇 Drop a comment below or visit [www.hnswatertech.com] to download our HPU Technical Whitepaper.

#MBBR #WastewaterTreatment #Biofilm #WaterEngineering #HNSWaterTech #EnvironmentalEngineering #WaterQuality #HPUmedia

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